DeFi (decentralised finance) refers to financial applications — exchanges, lending markets, savings products, derivatives — built on public blockchains using smart contracts, rather than run by a bank, broker, or other centralised institution. In principle, anyone with a wallet and an internet connection can access them directly.
DeFi removes some traditional middlemen, but it introduces its own specific risks: smart contract bugs, no customer support or chargebacks, exposure to extreme volatility, and products that can be far more complex than they first appear. It's genuinely useful technology, not automatically a safer or more profitable alternative to traditional finance.